With the increasing popularity of multimedia-capable computers, and the digitalization of multimedia in general, the importance of multimedia data embedding has become more important. In one type of multimedia data embedding, a key, also known as a watermark, is embedded into multimedia data, a process which is known as watermarking. This allows questions of ownership of a given piece of multimedia data—which may be widely distributed by virtue of the Internet, for example—to be resolved, by attempting to decode the key from the multimedia data. That is, by watermarking multimedia data, the data owner can determine whether a suspect piece of the multimedia data is his or hers by determining whether the watermark is present in the suspect data.
For example, a record company, prior to making its music selections available on the Internet for widespread purchase and use, can first watermark the data representing a music selection. If a site on the Internet is providing bootleg copies of the music selections, but claims that the copies are not in fact owned by the record company, the company can prove that they are indeed owned by it by showing that the watermark is present in the bootleg copies. Therefore, watermarking has applicability to audio multimedia, as well as other types of multimedia, such as image and video multimedia.
While conventional watermarking provides the advantage of being able to identify ownership of multimedia content, it is unable to identify who originally made a bootleg copy of the multimedia content. Thus, there is a need in the art for a mechanism to watermark a multimedia source for each transaction that affects the source. The watermarking must occur in such a manner as to identify the party participating in the transaction related to the multimedia source, for example, a purchaser of the multimedia source. Identifying parties related to the transaction is needed, because it provides a means for identifying a party who allows unauthorized copies to be made. Furthermore, there is a need in the art for means to indicate whether a given copy of a multimedia content source is registered or not registered, or to indicate the copying rights permitted of the user (for example, unlimited copying, one copy only, or no copying allowed).
However, prior art schemes of watermarking are ill suited to providing watermarks for the above-described transactions. Because watermarking in general is computationally intensive, a server responsible for transferring copies of a multimedia content source, and adding a watermark for every copy transferred, may become overwhelmed, necessitating the addition of more costly computing power. Furthermore, because the content source is typically compressed when stored on the server, it may be necessary to first decompress the source to add the watermark, which can also require additional computing power. For these and other reasons, there is a need for the present invention.